Baby salad is normally planted in a greenhouse and is harvested about 14-50 days after planting. Lettuce is normally planted in consecutive plantings so that there is a supply growing throughout the season. This means that as soon as the first planting has germinated and emerged the second planting is seeded. Leaf lettuces are normally harvested by hand into cartons in the field before being held in cold storage or shipped directly to wholesale distributors. Shelf life for lettuce is approximately two weeks so therefore it will be appreciated that time is of the essence in shipping the leaf lettuce to the wholesale distributors. However manually picking the leaf lettuce into cartons in the field is time consuming and inefficient. Use of a leafy vegetable harvester as described for example in U.S. Pat. No. 6,463,722 which is a mechanical harvester having a cutting assembly that cuts leafy vegetables such as baby greens in the field and deposits the cut leaves onto collection belts for ultimate location in storage bins is also time consuming and inefficient. Similar comments apply to mechanical leafy vegetable harvesters as described in U.S. Pat. Nos. 6,378,281, 6,173,559, 4,967,545 and 5,193,331.
Reference may be made to U.S. Pat. No. 5,964,081 which describes a baby greens harvester having a cutter/conveyor assembly fixed to a chassis so that the cutter/conveyor assembly may rotate about a generally horizontal axis. The baby greens after delivery by a conveyor belt to a cutting assembly are cut and the produce is then delivered into a produce box through a chute. However use of such a harvester was also found deficient because it could not be applied successfully to seedlings and was applicable only to fully grown produce in the field.
Reference also may be made to the November 2002 issue of the Australian periodical “Good Fruit and Vegetables” which describes a harvesting process wherein initially baby leaf lettuce leaves are grown in a seedling tray and taken to a harvesting machine and fed under a reciprocating blade which cuts off the leaves just above the tray surface. Detached leaves pass onto an upwardly inclined inspection or lift conveyor whereby they are inspected before delivery into containers. When full, the containers are taken to a cool room before transportation to a further processing facility by refrigerated vehicles. Use was made of a specially designed Williames Hi-Tech machine for harvesting the seedling leaves.
However it was found in practice using the above process that the harvesting machine was subject to frequent stoppages and there were gaps present between adjacent seedling trays which were mounted on a feed conveyor which transported the seedling trays to the reciprocating blade. This was because the feed conveyor comprised a stationary frame having a pair of chains at each side of the frame whereby each chain had a plurality of spaced lugs for pushing the seedling trays on the frame through to the reciprocating blade. When the gaps were present between adjacent trays it was found that often seedlings or leaves fell through the gaps located between spaced transverse frame members located on the conveyor frame. The gaps appeared because the spacing between the adjacent pusher lugs exceeded the length of the seedling trays which were of the order of 700 mm. Also the lift conveyor transporting the harvesting leaves from the cutting station was located above the reciprocating blade at a height which was excessive and thus this interfered with efficient removal of the harvested leaves from the reciprocating blade because the leaves jammed up on each side of the lift conveyor.